Battery Discharge, why is it important?

KaMoS

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I'm looking at doing a solar install using LiFePO4 batteries as energy storage. Everyone is telling me that Freedom Won batteries are best because of local support and having good discharge, among other things.

Is it worth it to pay a 20% premium for a battery that has double the discharge, 100A vs 200A? I know there are other factors to consider for batteries, but I'd like to get your opinions specifically regarding discharge and the advantages of having a battery with higher discharge.
 
Higher discharge means a better quality BMS and likely better tested cells to cope with the current requirements, that's if you can believe the spec sheets which often you can't... The more you're discharging lower than rated you're putting less strain on the battery, basically an over specced battery will last longer.

Depending on the alternative that's 20% cheaper, and if you can afford it, go freedom won as they're fantastic products.
 
You really need to get an understanding of your needs/loads vs what the batteries can do, e.g. for a small house load with gas water heating and gas cooking for example, your peak load would be a lot less than someone running multiple electric geysers and electric oven/stove.

The discharge rate limits how much power you can pull from the battery, e.g. will your battery be able to supply enough power when you turn on the kettle, or the kettle and the geyser at the same time, or will it shut down due to overload.

If it's a 48V battery you would say 100A * 48V = 4.8kW. Check the battery specs as well, some allow for peaks well above the continuous discharge limit, e.g. maybe it would allow 100A (4.8kW if 48V) constantly, but allow for bursts perhaps double that or higher.

If you're going to add multiple batteries in parallel, then remember that each battery will allow for the 100A limit, so if you put 2 batteries in parallel you'd effectively be able to do 2*100A = 200A (and 9.6kW if 48V battery) continuously.
 
The Greenrich batteries do up to 1.5C which means a 4.96kWh battery will provide 7.44kWh for 40min till its flat.
 
What happens to it's expected cycle life when run at 1.5C?
You will get to the limit of the warranty faster. So shorter lifecycle and the warranty only covers you for a certain amount of energy output from the battery.

Below is an extract from the performance warranty:

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Thanks for all the responses, this is very useful information.

In my scenario, I have gas piped into my house, so I have gas geysers and a gas stove. My main power hungry appliances are in the kitchen, Electric Oven, Microwave, Air Fryer, dishwasher, Washer / Dryer, and Kettle (can get rid of this, we have a stove-top for LS but it's just not as fast as electric).

I have a 7.5kVa generator that runs the entire house during load shedding, which I think is 50% efficient. So my takeaway from this thread is that I don't really need a high discharge battery. 1C - 1.5C should be okay as long as the capacity is enough. So if I have 10kW of storage, I can discharge @ 2kW / hour (0.5C) for 4 hours to 20% of my storage capacity. It's unlikely that this will happen at night, but at least now I think I have a good understanding of how to choose the right battery.
 
Thanks for all the responses, this is very useful information.

In my scenario, I have gas piped into my house, so I have gas geysers and a gas stove. My main power hungry appliances are in the kitchen, Electric Oven, Microwave, Air Fryer, dishwasher, Washer / Dryer, and Kettle (can get rid of this, we have a stove-top for LS but it's just not as fast as electric).

I have a 7.5kVa generator that runs the entire house during load shedding, which I think is 50% efficient. So my takeaway from this thread is that I don't really need a high discharge battery. 1C - 1.5C should be okay as long as the capacity is enough. So if I have 10kW of storage, I can discharge @ 2kW / hour (0.5C) for 4 hours to 20% of my storage capacity. It's unlikely that this will happen at night, but at least now I think I have a good understanding of how to choose the right battery.
Yes.

There are also batteries you can push to 90-95% usage which could give you an extra hour.

I am getting Greenrich batteries which are being installed this week. Will keep you updated on how it goes.
 
Thanks for all the responses, this is very useful information.

In my scenario, I have gas piped into my house, so I have gas geysers and a gas stove. My main power hungry appliances are in the kitchen, Electric Oven, Microwave, Air Fryer, dishwasher, Washer / Dryer, and Kettle (can get rid of this, we have a stove-top for LS but it's just not as fast as electric).

I have a 7.5kVa generator that runs the entire house during load shedding, which I think is 50% efficient. So my takeaway from this thread is that I don't really need a high discharge battery. 1C - 1.5C should be okay as long as the capacity is enough. So if I have 10kW of storage, I can discharge @ 2kW / hour (0.5C) for 4 hours to 20% of my storage capacity. It's unlikely that this will happen at night, but at least now I think I have a good understanding of how to choose the right battery.
Discharging a 10kWh battery at 2kw is only discharging it at 0.2C.

The bigger your battery bank, the less important the C rating becomes.

I started with a 9.5kWh battery bank and currently sitting on a 18.8kWh battery bank. During the night I'm only pulling 1kw from the battery so I'm discharging at less than 0.1C.

When it's charging from solar in the middle of the day its charging at ±0.3C or about 6kw.

The lower the charge or discharge rates, the better for the battery and the more cycles you will be able to get out of them. I'm hoping to increase my battery bank to 23kWh by the end of the year.
 
No. Untested with 0 track record but everyone is buying them.
Saw many installs with powerforum with them. No issues.

The supplier in SA is well known with a good reputation.

Yes but time will tell whether its was a good decision to buy these.
 
Discharging a 10kWh battery at 2kw is only discharging it at 0.2C.

The bigger your battery bank, the less important the C rating becomes.

I started with a 9.5kWh battery bank and currently sitting on a 18.8kWh battery bank. During the night I'm only pulling 1kw from the battery so I'm discharging at less than 0.1C.

When it's charging from solar in the middle of the day its charging at ±0.3C or about 6kw.

The lower the charge or discharge rates, the better for the battery and the more cycles you will be able to get out of them. I'm hoping to increase my battery bank to 23kWh by the end of the year.
Thanks for this. It makes sense. I am a qualified electrical engineer, but I qualified 16 years ago and am now more on the business side of things. I feel so out of the loop with solar tech. I'm trying really hard to gain more knowledge and a better understanding of all things solar. I appreciate all the feedback and help from everyone.
 
Depending on the alternative that's 20% cheaper, and if you can afford it, go freedom won as they're fantastic products.

I agree but Freedom Won batteries are around the R33 000 to R38000 per 5kW mark right now.
Dyness/Greenrich/Shoto 5kWh batteries are around R25 000.

That's a 30 to 40% premium for a better battery which is starting to get on the pricey side of things if one is trying to keep an install affordable.
 
I agree but Freedom Won batteries are around the R33 000 to R38000 per 5kW mark right now.
Dyness/Greenrich/Shoto 5kWh batteries are around R25 000.

That's a 30 to 40% premium for a better battery which is starting to get on the pricey side of things if one is trying to keep an install affordable.
Surely Pylon's at the same price point as the Greenrich are a winner?
 
If you are going to just buy 1 x 5kWh battery are you really going to pull more than 0.5C from it during loadshedding?

Or discharging at a constant 5kW. The pylontech is a brilliant battery and unless you really, really need to discharge at more than 0.5C on a 5kWh battery during load shedding then 5kWh is not going to last long. i do not see the point of harping on about the lower C rating of the pylontech.

And if you going with 5kWh of lithium, I'm assuming you going with a proper hybrid so if the grid is available it will just pull any shortfall from grid if its needs to.

I would still go with pylontech if I had to start over today.
 
Latching onto this thread for a similar decision between various batteries -
  • 1 x DYNESS 5.12KW LI-ION BATTERY 48V at about R26.5k; (7yr Warranty)
  • 1 x HUBBLE LITHIUM AM2 5.5KWH 51V BATTERY at about R30k; (10yr Warranty)
  • 1 x FELICITY 5.12KWH BATTERY at about R32k; (5yr Warranty)
(adding one more of the above later)

Or should one just consider 1 x FELICITY SOLAR 8.7KWH LI-ION BATTERY at about R38k?
 
Latching onto this thread for a similar decision between various batteries -
  • 1 x DYNESS 5.12KW LI-ION BATTERY 48V at about R26.5k; (7yr Warranty)
  • 1 x HUBBLE LITHIUM AM2 5.5KWH 51V BATTERY at about R30k; (10yr Warranty)
  • 1 x FELICITY 5.12KWH BATTERY at about R32k; (5yr Warranty)
(adding one more of the above later)

Or should one just consider 1 x FELICITY SOLAR 8.7KWH LI-ION BATTERY at about R38k?
I went for best bang-for-buck, and bought the Felicity Solar 12.5kWh for R47k. No regrets thus far.
 
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